Patent GB-1445158-A (GB)
Title: Apparatus for sewing a pocket piece to a garment
IPC: D05B65/00
Filed: 1973-09-07
Abstract: 1445158 Sewing SINGER CO 7 Sept 1973[9 April 1973] 42164/73 Heading DIG Apparatus or sewing pockets on garments includes a thread breakage detector and electric circuitry which causes the work-feeding mechanism to complete its cycle of movement then continue into another cycle until just before the point in the cycle where the thread broke. With the needle rethreaded sewing then recommences with an overlap of only a few stitches. Work folding is acomplished by a logic shaft assembly 84 (Fig. 4) carrying cams which move the pocket-folding work clamp assembly 74. This comprises a main folding plate 102, a holding plate assembly 104, a pair of side folding blades 106 and a front folding blade 108, each being operated in timed sequency by the logic shaft assembly 84. Work feeding is accomplished by a cam assembly 42 in which a pair of conjugate cams 46, 48 rotate about an axis 44 to cause two sets of links 52, 58 and 54, 60 carrying camfollowers 64, 66 respectively to move a stud 62 (Figure 2). The stud traces the outline of the desired seam line, and is attached to the work clamp assembly 74 so that the work is thus moved under the sewing machine 36a and follows the desired path. A thread breakage detector (Fig. 8) comprises a pulley 246 round which the needle thread passes twice. When the thread is moving the pulley is thus driven, together with the shaft 212 and a slotted drum 228 attached to the shaft. In turning, the slotted drum modulates the light received by a photo cell 244 from a source 240, and a signal is thus sent to a logic circuit stating whether or not the drum and hence the pulley is being driven by the thread. In operation the conjugate cams 46, 48 turn until an arm 148 on them actuates a switch 140 which brings a photo cell 142 (Figure 4) into circuit. When a "flag" 144 rotating with the main drive shaft 34 next interrupts the beam from a source 272 to the photocell 142 the sewing machine is started. This ensures that the machine is synchronised with the conjugate cams. At the corners of the pockets a speed control disc cam 50 engages switches 164, 166 to slow the sewing machine and the cam assembly. At the end of the sewing cycle an arm 170 on the cams actuates a switch 172 to stop the machine with its needle up, and trim the threads automatically. If a thread breaks during sewing the threadbreakage detector signals a logic circuit which only passes the signal on if the sewing machine is operating. The machine stops and the operator switches the electric circuitry to "Repair". The conjugate cams continue to drive the work feeder in the normal manner round its cycle of movement but a counter begins to count the number of revolutions of the main shaft 34. Knowing how many stitches are required during a complete sewing cycle, with one stitch per revolution of the shaft, the circuitry stops the conjugate cams when they have performed almost one whole cycle. The machine can thus be rethreaded and sewing started again with an overlap of only a few stitches. The apparatus is stated to be synchronised to such a degree that the overlapping stitches use the same needle holes as the previously sewn stitches.